The present invention relates to methods for inhibiting mammalian cellular replication. In a preferred embodiment, cell growth is inhibited in mammals for prevention and treatment of cancer. According to the present invention, cell growth is inhibited by binding of oligonucleotides to chromosomal sites normally bound by proteins, e.g. the p53 protein, whose normal function is to suppress uncontrolled cell division.
The process by which cellular replication occurs is complex, involving many steps and numerous factors including regulatory, cytoskeletal and polymerization proteins. However, some early steps in this complex process are known to be essential, for example, initiation of DNA replication.
In higher eukaryotes, DNA replication is thought to be initiated at many origins of replication present on chromosomal DNA. By virtue of homology to known viral origins of replication, some highly repeated eukaryotic origins of replication have been identified and sequenced (Jelinek et al. 1980 Proc. Natl. Acad. Sci. USA 77: 1398-1402).
Moreover some proteins have been identified which have a role in regulation of cell growth. For example many of the cellular protooncogenes are thought to have a normal role in cellular replication which is improperly executed when the protooncogene becomes mutated. The p53 gene is such a protooncogene. Normally the p53 protein appears to inhibit cell growth, however mutant p53 proteins can have an opposite effect upon cell growth, causing uncontrolled cell division and a variety of cancers, especially sarcomas, breast, brain, adrenal cortex, colon, lung and leukemic cancers (Finlay et al. 1989 Cell 57: 1083-1093; Ben-David et al. 1991 Cell 66: 831-834; and Haber et al. 1991 Cell 64: 5-8). Moreover, the p53 protein binds to DNA sites in a sequence-specific manner (Kern et al. 1991a Science 252: 1708-1711; Kern et al. 1991b Oncogene 6: 131-136). However, the significance of DNA binding by p53 protein relative to the role of p53 protein in cellular replication has not been established.
According to the present invention, cell growth is inhibited by site-specific oligonucleotide binding to DNA. Specifically, the site to which the oligonucleotide binds is a DNA site which can be bound by a protein repressor of cellular replication, e.g. the p53 protein.
Oligonucleotides have recently attracted attention as regulators of nucleic acid biological function. Naturally occurring complementary, or antisense, RNA are used by some cells to control protein expression or plasmid replication. For example, replication of some Escherichia coli plasmids, including the ColE1 plasmid, is regulated by an antisense RNA complementary to an RNA primer of ColE1 DNA replication (Lacatena et al. 1981 Nature 294: 623-626; Lin-Chao et al. 1991 Cell 65: 1233-1242).
Specific oligonucleotides have also been synthesized and tested as inhibitors of nucleic acid function. For example, splicing of a pre-mRNA transcript essential for Herpes Simplex virus replication has been inhibited with a linear oligonucleotide complementary to an acceptor splice junction (Smith et al., 1986, Proc. Natl. Acad. Sci. USA 83: 2787-2791). A linear oligonucleotide has also been used to inhibit protein synthesis of a human immunodeficiency virus (HIV) p24 protein (Agrawal et al. 1988 Proc. Natl. Acad. Sci. USA 85: 7079-7083). In another example, linear oligonucleotides were used to inhibit HIV replication in cultured cells. Linear oligonucleotides complementary to sites within or near the terminal repeats of the HIV retroviral genome and within sites complementary to certain splice junctions were most effective in blocking viral replication (Goodchild et al., 1988, Proc. Natl. Acad. Sci. USA 85: 5507-5511). Accordingly, the use of oligonucleotides as inhibitors of nucleic acid function has been limited to inhibition of functions such as RNA splicing, protein translation and viral replication via formation of Watson-Crick base pairs between an oligonucleotide and a nucleic acid template. The inhibition of cell growth by oligonucleotide binding has not been demonstrated.
An oligonucleotide binds to a target nucleic acid by forming hydrogen bonds between bases in the target and the oligonucleotide. Common B DNA has conventional adenine-thymine (A-T) and guanine-cytosine (G-C) Watson and Crick base pairs with two and three hydrogen bonds, respectively. The most common bonds that form between two complementary strands of RNA or DNA are Watson-Crick hydrogen bonds. However, other types of hydrogen bonding patterns are known wherein some atoms of a base which are not involved in Watson-Crick base pairing can form hydrogen bonds to another, third, nucleotide. For example, thymine (T) can bind to an A-T Watson-Crick base pair via hydrogen bonds to the adenine, thereby forming a T-AT base triad. Hoogsteen (1959, Acta Crystallography 12: 822) first described the alternate hydrogen bonds present in T-AT and C-GC base triads. More recently, G-TA base triads, wherein guanine can hydrogen bond with a central thymine, have been observed (Griffin et al., 1989, Science 245: 967-971).
Oligonucleotides have also been observed to bind and inhibit the function of a nucleic acid through non-Watson-Crick hydrogen bonding. For example, Cooney et al. (1988, Science 241: 456) disclose a 27-base single-stranded oligonucleotide which bound to a double-stranded nucleic acid via non-Watson-Crick hydrogen bonds. This oligonucleotide inhibited transcription of the human c-myc gene in a cell free, in vitro assay by binding to the c-myc promoter. In a review, Riordan et al. suggest that linear xe2x80x9cswitchbackxe2x80x9d oligonucleotides can be used to bind and inhibit the function of both strands of a double stranded nucleic acid target by Watson-Crick binding to one target strand and non-Watson-Crick binding to the other target strand (Riordan et al. 1991 Nature 350: 442-443. However, methods for inhibiting cell growth by either non-Watson-Crick or Watson-Crick binding of an oligonucleotide to a chromosomal binding site for a protein repressor of cellular replication are not available in the prior art.
Accordingly, the present invention represents an innovative step forward in the technology of cell cycle control by providing methods for inhibiting cellular replication through Watson-Crick and non-Watson-Crick binding of an oligonucleotide to chromosomal sites normally bound by protein repressors of cellular replication.
The present invention is directed to a method for inhibiting mammalian cell growth by providing a growing mammalian cell with a cell growth-inhibiting amount of an oligonucleotide comprising an RNA or a DNA which binds to a chromosomal binding site for p53 protein and thereby inhibiting said mammalian cell growth.
An additional aspect of the present invention provides a method of preventing or treating cancer by administering to a patient a therapeutically effective amount of an oligonucleotide comprising an RNA or a DNA which binds to a chromosomal binding site for p53 protein.
Another aspect of the present invention provides methods for inhibiting in vitro mammalian cell growth by contacting cultured mammalian cells with a cell growth inhibiting amount of an oligonucleotide comprising an RNA or a DNA which binds to a chromosomal binding site for p53 protein and thereby inhibiting said in vitro mammalian cell growth.
A further aspect of this invention is directed to a method of inhibiting cell growth in a mammal or a cultured mammalian cell by binding one of the present oligonucleotides to a chromosomal site for p53 protein either by Watson-Crick or non-Watson-Crick base pairs to form a double-helical or a triple-helical oligonucleotide-DNA complex, respectively.
Yet another aspect of the present invention provides a composition which includes a therapeutically effective amount of an oligonucleotide which can bind to a chromosomal binding site for p53 protein and a pharmaceutically acceptable carrier.
This invention relates to inhibition of cellular growth by oligonucleotides capable of binding to chromosomal sites normally bound by protein repressors of cell replication. Moreover, the present invention contemplates inhibition of cellular replication in mammals for the treatment and prevention of cancer as well as inhibition of cultured cell replication.
In particular, the present invention provides a method for inhibiting mammalian cell growth by providing growing cells with a cell growth-inhibiting amount of an oligonucleotide which can be an RNA or a DNA capable of binding to a chromosomal binding site for p53 protein, and thereby inhibiting mammalian cell growth. Moreover, according to the present invention, cell growth is preferably inhibited to treat or prevent cancer. In particular, this invention includes a method for preventing or treating cancer by administering to a patient a therapeutically effective amount of an oligonucleotide which can be an RNA or a DNA which binds to a chromosomal binding site for p53 protein.
In another embodiment, the present invention provides a method for inhibiting in vitro mammalian cell growth by contacting cultured mammalian cells with a cell growth-inhibiting amount of an oligonucleotide which is an RNA or a DNA capable of binding to a chromosomal binding site for p53 protein, and thereby inhibiting in vitro mammalian cell growth.
A sequence for a chromosomal binding site for p53 protein is known (Kern et al. 1991 Science 252: 1708-1711) and has been designated herein as a portion of SEQ ID NO:1. The sequence of SEQ ID NO:1, is depicted below:
Portions of SEQ ID NO:1 which can be chromosomal binding sites for p53 protein include, but are not limited to, SEQ ID NO:2-5, SEQ ID NO:7-9 and SEQ ID NO:13. SEQ ID NO:2 and 3 correspond to positions 56-83 of SEQ ID NO:1, while SEQ ID NO:4 and 5 correspond to positions 61-96 of SEQ ID NO:1. SEQ ID NO:7-9 correspond to positions 43-71, 70-95 and 100-121 of SEQ ID NO:1, respectively. SEQ ID NO:13 corresponds to positions 60-83 of SEQ ID NO:1. The sequences of SEQ ID NO:2-5, 7-9 and 13 are depicted below:
According to the present invention a chromosomal binding site for p53 protein is a domain within a chromosomal DNA having sufficient homology to a nucleotide sequence corresponding to either or both strands of SEQ ID NO:1, or a portion thereof, to permit detectable binding by p53 protein. The size of chromosomal site for p53 protein can be about 10 to about 200 bases or base pairs and is preferably about 10 to about 50 bases or base pairs.
Binding of p53 protein to a chromosomal DNA can be detected by any procedure available in the art, for example by immunoprecipitation, gel shift, DNA footprinting, methylation interference and similar assays, for example, as provided in Finlay et al. (1989 Cell 57: 1083-1093), Kern et al. (1991 Science 252: 1708-1711) and Sambrook et al.(1989, Molecular Cloning: A Laboratory Manual, Vols. 1-3, Cold Spring Harbor Press, NY). Moreover, recombinant p53 protein is available and can be obtained as a pure or semi-pure preparation (Friedman et al. 1990 Proc. Natl. Acad. Sci. USA 87: 9275; Hinds et al. 1989 J. Virol. 63: 739-746; Finlay et al. 1989 Cell 57: 1083-1093). Furthermore, anti-p53 antibodies and kits for detection of p53 protein can be obtained commercially (Oncogene Sciences, Uniondale, N.Y.). Accordingly one of skill in the art can readily utilize procedures and commercially available materials to determine whether p53 protein binds to a DNA having a given sequence, and thereby ascertain the degree of homology to SEQ ID NO:1 required by a chromosomal site to permit binding by p53 protein.
In a preferred embodiment, chromosomal DNA sites having greater than about 50%, and preferably greater than about 70%, homology to a portion of SEQ ID NO:1 are sufficiently homologous to be chromosomal sites permitting binding by p53 protein. Moreover, in an especially preferred embodiment, chromosomal sites are selected which can detectably bind at least 50% or more of the p53 protein bound by a DNA having SEQ ID NO:1-4, SEQ ID NO:7-9 or SEQ ID NO:13.
According to the present invention a patient is a human. Moreover a mammalian cell is an animal cell having a chromosomal DNA which encodes one or more copies of a binding site for p53 protein. Preferred mammalian cells are human, ape, monkey, mouse, rat, hamster, rabbit, cat, dog, horse, sheep, cow, bull and similar mammalian cells. Especially preferred mammalian cells of the present invention are human, monkey, mouse, rat and hamster cells.
Proliferation can be inhibited in numerous cells within a mammal, e.g., to prevent or treat cancer, by the methods of the present invention. In particular, this invention has utility for inhibiting growth of any cell type which can have a mutant or absent p53 protein or which can become cancerous when the p53 gene becomes mutated or is absent.
For example, according to the present invention, epithelial, mesothelial or endothelial cell growth can be inhibited in a mammal. Moreover, such cell types can be cancerous or non-cancerous mesangial, embryonic, brain, lung, breast, uterine, cervical, ovarian, prostate, adrenal cortex, skin, blood, brain, bladder, gastrointestinal, colon and related cells. In a preferred embodiment cellular proliferation can be inhibited in a mammal for treatment of a cancer. As used herein a cancer can be a carcinoma, sarcoma, breast, brain, adrenal cortex, colon, bladder, prostate, lung, leukemic or a related cancer.
According to the present invention, a mammalian cell having a mutant or absent p53 protein, or a mutant or absent p53 gene, can be identified by any known procedure, including by immunological, sequencing or hybridization procedures. For example, cells expressing mutant p53 protein can be distinguished from cells expressing wild type p53 protein by commercially available antibodies which can distinguish between these proteins (oncogene Science). Moreover, labeled nucleic acid probes homologous to genomic DNA encoding p53 protein can be used to identify changes in p53 mRNA or p53 DNA restriction fragment size by standard hybridization procedures (Sambrook et al.).
As used herein in vitro mammalian cellular proliferation means mammalian cell growth in culture. Moreover, mammalian cells whose proliferation can be inhibited in vitro by the methods of the present invention include any primary or immortalized cell line having a chromosomal DNA which encodes a binding site for p53 protein.
As used herein primary cell lines include cancerous and non-cancerous cells derived from any mammalian tissue specimen, for example, from mesangial, embryonic, brain, lung, breast, uterine, cervical, ovarian, prostate, adrenal cortex, skin, blood, brain, bladder, gastrointestinal, colon and related tissues. Immortalized cell lines can include human HeLa, colon 201, neuroblastoma, retinoblastoma and KB cell lines, mouse 3T3, L and MPC cell lines, hamster CHO and BHK 21 cell lines, a monkey BSC cell line and other cell types, for example mammalian cell types available from the American Type Culture Collection.
According to the present invention, cell growth is inhibited by binding one or more of the subject oligonucleotides to a p53 protein chromosomal binding site. Binding of the oligonucleotide has a similar effect upon cell growth as wild type p53 protein binding, i.e. inhibition of cell growth. Moreover, the methods of the present invention have been used to inhibit cell growth by up to 85%.
Without limiting the invention, binding of the present oligonucleotides may block access to that chromosomal binding site. Blocking access to this site can prevent factors, e.g. nucleic acids or proteins, involved in cellular or DNA replication from binding to or recognizing the chromosome at this site, from dissociating the two strands of chromosomal DNA at this site, from moving along the chromosome, or from recognizing signals encoded within the chromosome at this site. Therefore, blocking access to the chromosomal binding site for p53 protein may inhibit normal processes essential for cellular or DNA replication and thereby may inhibit cell growth.
Inhibition of cell growth by the present oligonucleotides can be observed in vitro or in vivo by any procedure available in the art. For example, in vitro inhibition can be detected by a reduction in number, or reduction in 3H-thymidine uptake, of cultured cells treated with an oligonucleotide. Inhibition of cell growth in vivo, e.g., in a patient with cancer, can be detected by any standard method for detecting tumors such as by X-ray or imaging analysis of a tumor size, or by observing a reduction in mutant p53 protein production or in the production of any known cell-specific or tumor marker within a biopsy or tissue sample.
As used herein a cell growth-inhibiting amount of an oligonucleotide for inhibiting cell growth or proliferation in a mammal is about 0.1 xcexcg to about 100 mg per kg of body weight per day and preferably about 0.1 xcexcg to about 10 mg per kg of body weight per day.
Moreover, a cell growth-inhibiting amount of an oligonucleotide for inhibiting in vitro cell proliferation or growth is about 0.1 xcexcM to about 100 xcexcM of the oligonucleotide, and preferably about 1.0 xcexcM to about 50 xcexcM of oligonucleotide.
In a preferred embodiment an oligonucleotide for inhibiting cellular replication according to the methods of the present invention is a deoxyoligonucleotide having 10 to 100 bases. Moreover, oligonucleotides having any one of the sequences of SEQ ID NO:2, SEQ ID NO:3, SEQ ID NO:4, SEQ ID NO:8, SEQ ID NO:9 or SEQ ID NO:12 are especially preferred oligonucleotides for inhibiting cell growth or for preventing and treating cancer.
However, according to the present invention any oligonucleotide having sufficient complementarity to detectably bind to either strand of SEQ ID NO:1, or a portion thereof, can be used to inhibit mammalian cell growth and to prevent or treat cancer.
Complementarity between nucleic acids is the degree to which the bases in one nucleic acid strand can hydrogen bond, or base pair, with the bases in a second nucleic acid strand. Hence, complementarity can sometimes be conveniently described by the percentage, i.e. proportion, of nucleotides which form base pairs between two strands or within a specific region or domain of two strands. For the present invention sufficient complementarity means that a sufficient number of base pairs exists between the subject oligonucleotides and a DNA having the sequence of either strand of SEQ ID No:1 to achieve detectable binding of the oligonucleotide.
Therefore a sufficient number, but not necessarily all, nucleotides in the present oligonucleotides can have hydrogen bonds to a DNA having the sequence of either strand of SEQ ID NO:1. The number of positions which are necessary to provide sufficient complementarity for binding of the subject oligonucleotides, can be detected by standard procedures including known hybridization and melting temperature determination procedures. Moreover, according to the present invention oligonucleotide binding can be detected by observing a decrease in cell proliferation, e.g., by measuring cell number or 3H-thymidine uptake. Accordingly the degree of complementarity between an oligonucleotide of the present invention and either strand of SEQ ID NO:1 need not be 100% so long as oligonucleotide binding can be detected. However, it is preferred that the present oligonucleotides have at least about 50% complementarity with either strand of SEQ ID NO:1. In an especially preferred embodiment sufficient complementarity is greater than 70% complementarity with either strand of SEQ ID NO:1.
Moreover, the degree of complementarity that provides detectable binding between the subject oligonucleotides and SEQ ID NO:1, is dependent upon the conditions under which that binding occurs. It is well known that binding between nucleic acid strands depends on factors besides the degree of mismatch between two sequences. Such factors include the GC content of the region, temperature, ionic strength, the presence of formamide and types of counter ions present. The effect that these conditions have upon binding is known to one skilled in the art. Furthermore, conditions are frequently determined by the circumstances of use. For example, the present oligonucleotides are used for inhibiting cell growth, accordingly no formamide will be present and the ionic strength, types of counter ions, and temperature correspond to physiological conditions. Therefore, oligonucleotides of the present invention are preferably selected by testing whether binding can occur to a DNA having SEQ ID NO:1 under physiological salt and temperature conditions when no formamide is present.
A thorough treatment of the qualitative and quantitative considerations involved in establishing binding conditions that allow one skilled in the art to design appropriate oligonucleotides for use under the desired conditions is provided by Beltz et al., 1983, Methods Enzymol. 100: 266-285 and by Sambrook et al.(1989, Molecular Cloning: A Laboratory Manual, Vols. 1-3, Cold Spring Harbor Press, NY).
Thus for the present invention, one of ordinary skill in the art can readily design a nucleotide sequence for the subject oligonucleotides which exhibits sufficient complementarity to detectably bind to a chromosomal binding site for p53 protein. As used herein xe2x80x9cbindingxe2x80x9d or xe2x80x9cstable bindingxe2x80x9d means that a sufficient amount of the oligonucleotide is bound or hybridized to this site to permit detection of that binding.
Binding between a DNA encoding a chromosomal site for p53 protein and an oligonucleotide can be detected by any procedure known to one skilled in the art, including both functional or physical binding assays.
Binding may be detected functionally by determining whether binding has an observable effect upon cell growth, e.g., by observing a reduced number of cultured cells or a reduced 3H-thymidine uptake into cultured cells treated with the present oligonucleotides relative to untreated cells.
Physical methods for detecting binding between complementary strands of DNA or RNA are well known in the art, and include standard Southern and Northern hybridization, light absorption detection, gel shift, DNA footprinting, alkylation interference and related procedures (as provided for example in Sambrook et al.).
According to the present invention oligonucleotides can bind to a chromosomal site by conventional Watson-Crick base pairing or by non-Watson-Crick base pairing.
Watson-Crick base pairing occurs through formation of base pairs between adenine (A) and thymine (T) or uracil (U) or suitable analogs thereof, and through formation of base pairs between guanine (G) and cytosine (C), or suitable analogs thereof. Moreover, Watson-Crick base pairing can occur when oligonucleotide nucleotides are oriented in an opposite, or anti-parallel, 5xe2x80x2 to 3xe2x80x2 direction relative to nucleotides within a chromosomal site. Binding of an oligonucleotide by Watson-Crick base pairing can be detected or assayed by any known hybridization procedure (Sambrook et al.)
In contrast to Watson-Crick base pairing, non-Watson-Crick hydrogen bonding occurs when oligonucleotide and chromosomal site nucleotides have the same, or parallel, 5xe2x80x2 to 3xe2x80x2 orientation. Moreover, when the subject oligonucleotides bind by non-Watson-Crick hydrogen bonding the strands of the chromosomal site do not dissociate and a three stranded or triple-helical oligonucleotide-DNA complex forms. Accordingly, in another embodiment the subject oligonucleotides bind by non-Watson-Crick base pairing to form a triple-helical oligonucleotide-DNA complex, for example as provided in Beal et al. (1991 Science 251: 1360-1363), Mahler et al. (1990, Biochemistry 29: 8820-8826), Haner et al. (1990 Biochemistry 29: 9761-9765), Maher et al. (1989, Science 245: 725-730), Hoogsteen (1959, Acta Crystallography 12: 822), Griffin et al. (1989, Science 245: 967-971), Cooney et al. (1988 Science 241: 456-459) or the like.
In a preferred embodiment, non-Watson-Crick binding of the present oligonucleotides occurs through formation of hydrogen bonds between one of the present oligonucleotides and a double-stranded chromosomal DNA site. In an especially preferred embodiment, non-Watson-Crick binding of the present oligonucleotides occurs through formation of hydrogen bonds between an oligonucleotide T and an A within an AT chromosomal site base pair, or between an oligonucleotide C and a G within a GC chromosomal site base pair, to form T-AT and C-GC base triads, respectively.
Binding of an oligonucleotide by non-Watson-Crick hydrogen bonding to form a triple-helix oligonucleotide-DNA complex can be observed or assayed by art recognized procedures. Such procedures can include oligonucleotide-directed affinity cleavage, DNase I footprinting, methylase interference and related procedures (Moser et al. 1987 Science 238: 645; Strobel et al. 1988 J. Am. Chem. Soc. 110: 7927; Cooney et al. 1988 Science 241: 456-459).
Therefore, the skilled artisan can readily utilize the teachings of the present invention to make an oligonucleotide having the necessary structural features to bind a chromosomal site with either Watson-Crick or non-Watson-Crick base pairs.
The present oligonucleotides are single-stranded DNA or RNA having nucleotide bases guanine (G), adenine (A), thymine (T), cytosine (C) or uracil (U), or any nucleotide analog that is capable of hydrogen bonding by either Watson-Crick or non-Watson-Crick hydrogen bonds. Nucleotide analogs include pseudocytidine, isopseudocytidine, 3-aminophenyl-imidazole, 2xe2x80x2-O-methyl-adenosine, 7-deazadenosine, 7-deazaguanosine, 4-acetylcytidine, 5-(carboxy-hydroxylmethyl)-uridine, 2xe2x80x2-O-methylcytidine, 5-carboxymethylaminomethyl-2-thioridine, 5-carboxymethylamino-methyluridine, dihydrouridine, 2xe2x80x2-O-methyluridine, 2xe2x80x2-O-methyl-pseudouridine, beta, D-galactosylqueosine, 2xe2x80x2-O-methylguanosine, inosine, N6-isopentenyladenosine, 1-methyladenosine, 1-methyl-pseudouridine, 1-methylguanosine, 1-methylinosine, 2,2-dimethylguanosine, 2-methyladenosine, 2-methylguanosine, 3-methylcytidine, 5-methylcytidine, 5-methyluridine, N6-methyl-adenosine, 7-methylguanosine, 5-methylamino-methyluridine, 5-methoxyaminomethyl-2-thiouridine, xcex2-D-mannosylqueosine, 5-methoxycarbonylmethyluridine, 5-methoxyuridine, 2-methyl-thio-N6-isopentenyladenosine, N-(9-beta-D-ribofuranosyl-2-methylthiopurine-6-yl)-carbamoyl)threonine, N-(9-beta-D-ribofuranosylpurine-6-yl)-N-methylcarbamoyl)threonine. When possible, either ribose or deoxyribose sugars can be used with these analogs. Nucleotide bases in an xcex1-anomeric conformation can also be used in the oligonucleotides of the present invention.
Preferred nucleotide analogs are unmodified G, A, T, C and U nucleotides; pyrimidine analogs with lower alkyl, lower alkoxy, lower alkylamine, phenyl or lower alkyl substituted phenyl groups in the 5 position of the base and purine analogs with similar groups in the 7 or 8 position of the base. Especially preferred nucleotide analogs are 5-methylcytosine, 5-methyluracil, diaminopurine, and nucleotides with a 2xe2x80x2-O-methylribose moiety in place of ribose or deoxyribose.
As used herein lower alkyl, lower alkoxy and lower alkylamine contain from 1 to 6 carbon atoms and can be straight chain or branched. These groups include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tertiary butyl, amyl, hexyl and the like. A preferred alkyl group is methyl.
The present oligonucleotides can be made by any of a myriad of procedures known for making DNA or RNA oligonucleotides. For example, such procedures include enzymatic synthesis and chemical synthesis.
Enzymatic methods of DNA oligonucleotide synthesis frequently employ Klenow, T7, T4, Taq or E. coli DNA polymerases as described in Sambrook et al. Enzymatic methods of RNA oligonucleotide synthesis frequently employ SP6, T3 or T7 RNA polymerase and reverse transcriptase as described in Sambrook et al. To prepare oligonucleotides enzymatically requires a template nucleic acid which can either be synthesized chemically, or be obtained as mRNA, genomic DNA, cloned genomic DNA, cloned cDNA or other recombinant DNA. Some enzymatic methods of DNA oligonucleotide synthesis can require an additional primer oligonucleotide which can be synthesized chemically. Finally, oligonucleotides can be prepared by polymerase chain reaction (PCR) techniques as described, for example, by Saiki et al., 1988, Science 239:487.
Chemical synthesis of oligonucleotides is well known in the art and can be achieved by solution or solid phase techniques. Moreover, oligonucleotides of defined sequence can be purchased commercially or can be made by any of several different synthetic procedures including the phosphoramidite, phosphite triester, H-phosphonate and phosphotriester methods, typically by automated synthesis methods.
Synthetic oligonucleotides may be purified by polyacrylamide gel electrophoresis, or by any of a number of chromatographic methods, including gel chromatography and high pressure liquid chromatography. To confirm a nucleotide sequence, oligonucleotides may be subjected to DNA sequencing by any of the known procedures, including Maxam and Gilbert sequencing, Sanger sequencing, capillary electrophoresis sequencing the wandering spot sequencing procedure or by using selective chemical degradation of oligonucleotides bound to Hybond paper. Sequences of short oligonucleotides can also be analyzed by plasma desorption mass spectroscopy or by fast atom bombardment (McNeal, et al., 1982, J. Am. Chem. Soc. 104: 976; Viari, et al., 1987, Biomed. Environ. Mass Spectrom. 14: 83; Grotjahn et al., 1982, Nuc. Acid Res. 10: 4671). Sequencing methods are also known in the art for RNA oligonucleotides.
The present invention also contemplates derivatization or chemical modification of the subject oligonucleotides with chemical groups to facilitate cellular uptake. For example, covalent linkage of a cholesterol moiety to an oligonucleotide can improve cellular uptake by 5- to 10-fold which in turn improves DNA binding by about 10-fold (Boutorin et al., 1989, FEBS Letters 254: 129-132). Other ligands for cellular receptors may also have utility for improving cellular uptake, including, e.g. insulin, transferrin and others. Similarly, derivatization of oligonucleotides with poly-L-lysine can aid oligonucleotide uptake by cells (Schell, 1974, Biochem. Biophys. Acta 340: 323, and Lemaitre et al., 1987, Proc. Natl. Acad. Sci. USA 84: 648). Certain protein carriers can also facilitate cellular uptake of oligonucleotides, including, for example, serum albumin, nuclear proteins possessing signals for transport to the nucleus, and viral or bacterial proteins capable of cell membrane penetration. Therefore, protein carriers are useful when associated with or linked to the oligonucleotides of this invention.
Accordingly, the present invention contemplates derivatization of the subject oligonucleotides with groups capable of facilitating cellular uptake, including hydrocarbons and non-polar groups, cholesterol, poly-L-lysine and proteins, as well as other aryl or steroid groups and polycations having analogous beneficial effects, such as phenyl or naphthyl groups, quinoline, anthracene or phenanthracene groups, fatty acids, fatty alcohols and sesquiterpenes, diterpenes and steroids.
In accordance with the present invention, modification in the phosphodiester backbone of oligonucleotides is also contemplated. Such modifications can aid uptake of the oligonucleotide by cells or can extend the biological half-life of such oligonucleotides. For example, oligonucleotides may penetrate the cell membrane more readily if the negative charge on the internucleotide phosphate is eliminated. This can be done by replacing the negatively charged phosphate oxygen with a methyl group, an amine or by changing the phosphodiester linkage into a phosphotriester linkage by addition of an alkyl group to the negatively charged phosphate oxygen. Alternatively, one or more of the phosphate atoms which is part of the normal phosphodiester linkage can be replaced. For example, NHxe2x80x94P, CH2xe2x80x94P or Sxe2x80x94P linkages can be formed. Accordingly, the present invention contemplates using methylphosphonates, phosphorothioates, phosphorodithioates, phosphotriesters and phosphorus-boron (Sood et al., 1990, J. Am. Chem. Soc. 112: 9000) linkages. The phosphodiester group can be replaced with siloxane, carbonate, acetamidate or thioether groups. These modifications can also increase the resistance of the subject oligonucleotides to nucleases. Methods for synthesis of oligonucleotides with modified phosphodiester linkages are reviewed by Uhlmann et al. (1990, Chemical Reviews 90: 543-584).
A further aspect of this invention provides pharmaceutical compositions containing the subject oligonucleotides with a pharmaceutically acceptable carrier. In particular, the subject oligonucleotides are provided in a therapeutically effective amount of about 0.1 xcexcg to about 100 mg per kg of body weight per day, and preferably of about 0.1 xcexcg to about 10 mg per kg of body weight per day, to bind to a nucleic acid in accordance with the methods of this invention. Dosages can be readily determined by one of ordinary skill in the art and formulated into the subject pharmaceutical compositions.
As used herein, xe2x80x9cpharmaceutically acceptable carrierxe2x80x9d includes any and all solvents, dispersion media, coatings, antibacterial and antifungal agents, isotonic and absorption delaying agents, and the like. The use of such media and agents for pharmaceutical active substances is well known in the art. Except insofar as any conventional media or agent is incompatible with the active ingredient, its use in the therapeutic compositions is contemplated. Supplementary active ingredients can also be incorporated into the compositions.
The subject oligonucleotides can be provided to a mammalian cell by topical or parenteral administration, for example, by intraveneous, intramuscular, intraperitoneal, subcutaneous or intradermal route, or when suitably protected, the subject oligonucleotides can be orally administered. The subject oligonucleotides may be incorporated into a cream, solution or suspension for topical administration. For oral administration, oligonucleotides may be protected by enclosure in a gelatin capsule. Oligonucleotides may be incorporated into liposomes or liposomes modified with polyethylene glycol for parenteral administration. Incorporation of additional substances into the liposome, for example, antibodies reactive against membrane proteins found on specific target cells, can help target the oligonucleotides to specific cell types.
Topical administration and parenteral administration in a liposomal carrier is preferred.